Method of cleaning oil wells



Dec. 26, 1961 v H. J. WEAVER 3,014,531

METHOD OF CLEANING OIL WELLS Filed Nov. 5, 1958 flu 'fi d Weaver INVENTOR.

BY %%-wam MAM rods.

Texas 7 Filed Nov. 5, 1958, Ser. No. 772,045 Claims. (Cl. 166--41) This invention relates to a method of cleaning oil wells. More particularly, this invention relates to such a method for removal of paraffin from oil wells.

There has been considerable difiiculty in producing oil having parafiin as a constituent because of the accumulation of parafiin deposits normally on the inside of the tubing and, if a pumping string is used, on the outside of the sucker rods. Ordinarily, the temperature at the bottom of the hole is sufficient to keep the paraffin in solution. As the oil moves up the tubing, however, it is cooled, for example, when passing through a cold water sand, so that the parafiin solidifies and is deposited on the tubing and on the sucker rods. Ordinarily, this occurs between about 1500 feet and 1800 feet although, of course, it may occur at other depths. This accumulation builds up until such time as the well must be shut down and the paraflin deposits removed.

One method of removing these deposits is by the socalled hot oil method in which cold oil in the tubing is displaced by introducing hot oil into the tubing and letting it stand in the tubing for a length of time to melt the paraffin deposits. The pump is then started up'and the oil is pumped out to the surface. Such a processis disclosed in United States Patent No. 2,300,348 granted October 27, 1942 on the application of F. E. Dana.

This method is disadvantageous in that it requires a considerable length of time to melt the paraffin deposits. Also, this method does not satisfactorily melt the parafiin deposits in the tubing and on the sucker rods and much of the parafiin melted resolidifies before it can be pumped out of the tubing since the melted parafiin is not removed from the place of its deposition as it is melted and the hot oil cools considerably and redeposits paraifin as it cools.

, A still further method of removing parafiin deposits involves introducing hot oil in the annular space between the tubing and the casing which requires a considerable volume of hot oil and heating up of the entire tubing string which is wasteful and requires considerable time and does not satisfactorily remove parafiin from the sucker rods.

Another method of removing paraffin deposits is by mechanical means, for example, the use of scrapers and the like in which the sucker rods, and many times the tubing, must be removed which requires a considerable amount of time;

It is therefore an object of the present invention to provide an improved method of cleaning oil wells of paraffin deposits which quickly and eificicntly melts and removes accumulations of paraflin in the tubing and on the sucker Still a further object is the provision of a method of quickly melting paraflin accumulations on the inside of tubing walls and sucker rods by continuously introducing hot oil into the tubing and discharging it from the tubing at a point below the lower paraffin level so that parafin is melted and removed from the tubing before it can resolidify.

Still a further object of the present invention is the provision of a method of melting paraffin accumulations on tubing walls and sucker rods in well bores which comprises introducing hot oil into the tubing and discharging it from the tubing ata point below the lower parafiin level so'that parafiin is melted and removed from the tubing before it can resolidify,.the discharged hot oil having parafiin in solution flowing to the bottom of the hole where f nited rates Patent" the temperature is sufficient to maintain the paraffin in solution, and then pumping oil out the tubing and recovering the hot oil introduced into the tubing.

Other and further objects, features and advantages will be apparent from the following description of a presently preferred embodiment of the invention. The method of the invention is best described in connection with suitable apparatus for performing the method as shown on the accompanying drawing, where like character references designate like parts throughout the several views, and where FIGURE 1 is a schematic diagram illustrating a well provided with the necessary equipment to carry out the present invention, the casing of the well being shown on an enlarged scale, and

FIGURE 2 is an enlarged View, in sectional elevation, illustrating a presently preferred form of release valve.

Referring now to the drawing, and particularly to FIGURE 1, the numeral in designates a well casing 10 provided, with the tubing 12 into which the sucker rods 14 are disposed, to the lower end of which is secured the traveling valve 16, and to the lower end of the tubing 12 is provided the standing valve 18. The sucker rod or pumping string 14 extends out the upper well head connection 2t and is secured to the walking beam 22 of the pumping assembly generally indicated by the reference numeral 24. The discharge pipe 26 provided with the valve 28 is secured to the well head connection 29 so that as the walking beam 22 is actuated, the sucker rods 14 are reciprocated in the tubing 12 and oil is pumped up the tubing and out the pipe 26 in the usual manner.

The above described elements represent a typical pumping assembly which functions in a well known manner and, accordingly, no more description thereof is deemed necessary.

In the present invention a release valve 30 is secured to the tubing 12 at a point below the lower parafiin level so that hot oil introduced into the tubing 12 melts the paraffin accumulated on the inside wall of the tubing and on the sucker rods 14 and is then discharged from the tubing. This removes all parafiin accumulations and prevents resolidification of paraffin in the tubing.

Preferably, a portable unit is provided for introducing the hot oil down into the tubing 12. For this purpose, a truck 32 is provided which includes the tank 34, the pump 36 connected by the line 38 from the tank 34 and by the line 42 to the heater 40 for pumping oil from the tank 34 to the heater 40 and where it is heated and then pumped in line 44 through the valved inlet 46 into the pipe 26 for introducing it into the tubing 12.

The details of the release valve 30 are best illustrated in FIGURE 2, to which reference is now made. The release valve 30 includes the valve seat 50 which is threaded into the fitting 52 welded or otherwise secured tothe tubing 12, the fitting 52 being provided with the passage 54 communicating with the internal passage 56 in the valve seat 50. A ball type valve element 58 is yieldingly held upwardly against the valve seat 50 by the valve plunger 60 which is held in an upward position by the spring guide adaptor 62 which includes the downwardly facing shoulder 64 against which the compression spring 66 bears which thereby yieldingly maintains the ball valve element 58 seated against the valve seat 50.

In order to maintain the desired compression in the spring 66 so that the release valve will release at a predetermined pressure, a spring adaptor 68 hearing against the lower end of the compression spring 66 is supported in position by the set screw 70 threaded in the lower end of the bottom plug 72 which, in turn, is threaded into the generally tubularly-shaped body 74 of the release valve 30.

Thus, by adjusting the set screw 79, the desired force Patented Dec. 26,1Q6i

is applied against the ball valve element 58 so that it will release under a predetermined minimum pressure.

In order to avoid torquing the spring 66 when adjusting the set screw 70, a ball type antifriction contact element 76 is provided for contacting the bottom spring adaptor 68 with the set screw 70 so that relative rotation between the set screw and the bottom spring adaptor 68 is provided.

In order to avoid tampering with the adjustment of the release valve 30 by means of adjusting the set screw 70, preferably, in use, the threaded bore 78 into which the set screw 70 is placed and the bore 80 in communication therewith is closed, for example, such as filling with lead.

The release valve, of course, is suitably packed off and includes the packing ring 82 disposed adjacent the upper valve outlets 84, which packing ring 82 is integral with the packing sleeve 86 which is supported bythe sleeve 88 welded or otherwise secured to the tubular body 74. The packing ring 82 includes the valve outlets 83 in communication with the valve outlets 84 of the tubular body 74. Also provided are the chevron type packing elements 90 which are held in place by the packing adaptor 92 against the packing adaptor 94 slidably surrounding the plunger 60 and supported in position by the guide washer 96.

Thus, when the pressure in the passages 54 and 56 overcomes the preset pressure of the release valve 30, oil is discharged out the outlets or ports 84 and ordinarily flows to the bottom of the Well 10.

Preferably, in operation, the release valve 39 is preset so that during normal pumping operations oil within the tubing 12 is not discharged out the release valve 30, but when pumping a hot fluid or a deparaflining fluid into the tubing, above this pressure, it is discharged out the tubing.

Normal well pumping operations of the well are stopped and the method of the invention is then performed by pumping hot fluid or any other deparafiining fluid down the tubing 12 until such time as a quantity thereof is circulated through the parafl'in accumulation in the tubing 12 and on the sucker rods 14 suflicient to melt the paraffin accumulation. The hot fluid or deparaflining fluid is continuously discharged out the release valve 30 and passes to the fluid level in the bottom of the casing 10. The continuous flow of the hot fluid or deparafiining fluid through the paraffin accumulation continuously melts and carries away the melted paraflin so that walls of the tubing 12 and the sucker rods are completely cleaned of paraffin deposits. The fluid in the bottom of the casing is quite hot and keeps the melted parafiin in solution.

After a relatively short length of time, for example, about thirty minutes in most wells, the pump 24 is actu ated by any suitable means which pumps the oil within the tubing 12 up out the tubing and into the pipe 26 in the usuaLmanner. The hot fluid or deparaflining fluid is eventually pumped out the well and recovered. When the pump 24 is actuated and oil within the tubing is again pumped out of the well, paraflin will again be de posited which will again require deparaflining the well after an accumulation of paraffin has again built up in the well.

Preferably, the hot fluid or deparaflining fluid is heated oil which is obtained from a tank on the particular lease on which the well is located, and is eventually recovered as previously described.

Preferably, in performing the process, oil is first obtained from a tank on the lease and placed into the tank 34 on the truck 32. The oil is pumped from the tank 34 in line 38 by the pump 36 into line 42 to the heater 40 and into the line 44 through the connection 46 into the tubing 12. Of course, other arrangements may be utilized as desired for introducing thehot oil into the tubing 12.

Aspreviously mentioned, sincethe accumulation of paraflin in the tubing and on the sucker rods vary in different oil fields, the amount of hot fluid or deparaflining fluid required will vary. Also, the volume of hot fluid or deparaffining fluid depends upon the tubing size, sucker rod size, depth of paraflin deposits and volume or accumulation of paraflin to be melted. Ordinarily, the paraflin accumulation can readily and easily be estimated from past cleaning operations. In addition, there is some obstruction to the flow of hot fluid or deparaffining fluid due to the paraffin accumulation. Ordinarily, is using hot oil, volumes up to 25 barrels are sufficient and, preferably, the rate of pumping should be varied to meet the conditions at the particular well site.

In actual use, it has been found satisfactory for the truck to have a 50 barrel tank, a high pressure pump up to 4000 p.s.i., and a direct fired heater 40 having temperatures up to 300 F. maximum. With this equipment the hot oil volume, temperature and pressure are sutficient to insure thorough cleaning under practically all conditions. Obviously, of course, other conditions may be employed.

The simplicity, quickness and ease of performing the method which completely removes the parafiin deposits seems apparent. The only thing required downhole is the addition of the release valve 30 to the tubing. This may be attached at any time when the tubing is pulled or when the tubing is initially placed in the well if it is known that paraffin accumulations will occur in the well. This, of course, is determined by the paraflin content of the oil from the formation being produced.

Thus, the present invention is based upon introducing deparaffining fluid down the tubing, continuously flowing it past the parafiin accumulations thereby melting the accumulated paraflin, and discharging the fluid and melted paraffin out the tubing below the lower parafiin accumulation level. This effectively cleans the tubing and sucker rods of the paraffin. The present invention does not require the time consuming procedure of letting the hot oil stand in the tubing adjacent the parafiin deposit, nor does it rely upon introducing hot oil down the annular space between the tubing and casing in order to heat up the entire length of the tubing and the oil therein, nor does it require time-consuming mechanical cleaning. None of these last-mentioned methods completely clean the tubing and sucker rods. Paraffin deposits more readily on paraffin than on a clean surface, so that ineffective and unsatisfactory cleaning is obtained by these methods in which paraflin accumulates sooner than when cleaning by the present method.

While the invention has been described particularly with reference to pumping wells, the method may also be applied to flowing wells by providing a release valve at an appropriate place in the tubing. In this situation, the pump pressure at the surface must be suflicient to force the hot oil down into the tubing against the existing bottom hole pressure and out the release valve. The injection of hot oil, of. course, is stopped When an adequate amount has been introduced into the tubing. Flowing of the well is resumed so as to bring to the surface oil in the well and eventually the oil discharged into the annular space.

The method may also be applied to wells operating by gas lift and other recovery systems.

The present invention, therefore, is well suited and adapted to attain the objects and ends and has the advantages and features mentioned as well as others inherent therein.

While a presently preferred method has been described for the purpose of disclosure, changes in the details and steps of the method may be made which are within the spirit of the invention as defined by the scope of the appended claims.

ing resident oil therein to remove deposits of paraffin therefrom comprising, introducing a deparafiining fluid into the upper portion of the tubing to form a downwardly moving fluid column in the tubing, contacting and moving the resident oil downwardly by the downwardly moving fluid column, continuously discharging the resident oil and deparafiining fluid downwardly in the well from the tubing at a point below the deposits of paraflin, continuing to introduce the deparaflining fluid into the tubing to form said fluid column and to continuously move said fluid column past the paraffin deposits until the paraffin deposits are substantially completely removed and the removed paraifin has gone into solution therein, and continuing to discharge the downwardly moving column of (leparaflining fluid with paraffin in solution therein from the tubing at the point below the paraffin deposits.

2. The method of claim 1 where the deparaffining fluid comprises a heated hydrocarbon oil.

3. A method of treating the tubing of an oil well to remove deposits of paraflin therefrom comprising, introducing a deparaflining fluid into the upper portion of the tubing, flowing the deparaflining fluid past the paraffin deposits until the pa-raflin deposits are substantially completely removed and the removed paraflin has gone into solution therein, and discharging the deparafiining fluid with paraflin in solution therein from the tubing at a point below the paraffin deposits and flowing the discharged fluid downwardly externally of the tubing toward the bottom of the well.

4. The method of claim 3 in which the deparaflining fluid comprises a heated hydrocarbon oil.

5. A method of treating the tubing of an oil Well to remove deposits of paraffin therefrom comprising, introducing a deparaflining fluid into the upper portion of the tubing, flowing the deparaffining fluid past the parafin deposits until the paraflin deposits are substantially completely removed and the removed paraflin has gone into solution therein, and discharging the deparafiining fluid with paraifin in solution therein from the tubing at a point below the paraifin deposits and flowing the discharged fluid externally of the tubing downwardly toward the bottom of the well, and thereafter recovering to the surface through the tubing the deparaflining fluid discharged from the tubing as aforesaid.

6. The method of claim 5 in which the deparaflining fluid comprises a heated hydrocarbon oil.

7. In an oil well provided with casing, tubing disposed in the casing and a pumping string disposed in the tubing, the method of removing paraffin deposits in the tubing and on the pumping string comprising, introducing a deparaflining fluid into the upper portion of the tubing, flowing the deparaffining fluid past the paraflin deposits until the paraffin deposits are substantially completely removed and the removed paralfin has gone into solution therewith, and discharging the deparaflining fluid with the paraflin in solution therein from the tubing at a point below the paraflin deposits and downwardly in the space between the tubing and casingv 8. The method of claim 7 where the deparafiining fluid comprises a heated hydrocarbon oil.

9. In an oil well provided with casing, tubing disposed in the casing and a pumping string disposed in the tubing, the method of removing paraflin deposits in the tubing and on the pumping string comprising, introducing a deparaffining fluid into the upper portion of the tubing, flowing the deparaffining fluid past the paraflin deposits until the parafin deposits are substantially completely removed and the removed paraflin has gone into solution therewith, discharging the deparaflining fluid with the paraifin in solution therein from the tubing at a point below the paraflin deposits to the fluid level in the space between the tubing and casing downwardly toward the bottom of the well, and thereafter recovering to the surface through the tubing the deparaflining fluid discharged as aforesaid by actuating the pumping string disposed in the tubing.

10. The method of claim 9 where the deparaflining fluid is a heated hydrocarbon oil.

References Cited in the file of this patent UNITED STATES PATENTS 2,360,348 Dana Oct. 27, 1942 2,415,729 Dana Feb. 11, 1947 2,704,979 Van Willigen Mar. 29, 1955 2,765,850 Allen Oct. 9, 1956 2,770,307 Deerdoff Nov. 13, 1956 

1. A METHOD OF TREATING THE TUBING OF AN OIL WELL HAVING RESIDENT OIL THEREIN TO REMOVE DEPOSITS OF PARAFFIN THEREFROM COMPRISING, INTRODUCING A DEPARAFFINING FLUID INTO THE UPPER PORTION OF THE TUBING TO FORM A DOWNWARDLY MOVING FLUID COLUMN IN THE TUBING, CONTACTING AND MOVING THE RESIDENT OIL DOWNWARDLY BY THE DOWNWARDLY MOVING FLUID COLUMN CONTINUOUSLY DISCHARGING THE RESIDENT OIL AND DEPARAFFINING FLUID DOWNWARDLY IN THE WELL FROM THE TUBING AT A POINT BELOW THE DEPOSITS OF PARAFFIN, CONTINUING TO INTRODUCE THE DEPARAFFINING FLUID INTO THE TUBING TO FORM SAID FLUID COLUMN AND TO CONTINUOUSLY MOVE SAID FLUID COLUMN PAST THE PARAFFIN DEPOSITS UNTIL THE PARAFFIN DEPOSITS ARE SUBSTANTIALLY COMPLETELY REMOVED AND THE REMOVED PARAFFIN HAS GONE INTO SOLUTION THEREIN, AND CONTINUING TO DISCHARGE THE DOWNWARDLY MOVING COLUMN OF DEPARAFFINING FLUID WITH PARAFFIN IN SOLUTION THEREIN FROM THE TUBING AT THE POINT BELOW THE PARAFFIN DEPOSITS. 